Direct Evidence of Dissociation Hydrogen Molecules Adsorption Through Spillover Effect by Ti Catalyst
Jhih-Wei Chen1*, Camilla Coletti2, Stefan Heun3, Min-Fa Lin1, Chia-Hao Chen4, Chung-Lin Wu1
1Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
2Center for Nanotechnology Innovation @ NEST, NEST, Pisa 56127, Italy
3NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, NEST, Pisa 56127, Italy
4National Synchrotron Radiation Research Center (NSRRC), NSRRC, HsinCHu 30076, Taiwan
* Presenter:Jhih-Wei Chen,
Recently, researcher has found the decorating transition metals (TMs) can not only increase the adsorption sites, but also initiates the hydrogen spillover effect. The spillover effect will result in the H2 molecules dissociating on adsorbate atoms and then attaching to the graphene, and causes the energy gap opening in electronic structure. So far, the electronic evidence of spillover effect at room temperature is still lacking. In this study, we have demonstrated the dissociated molecular hydrogen spills on the catalytically site of titanium (Ti) adsorbate and chemisorbed with pz orbital of C atoms, which causes the orbital hybridization from sp2 to sp3. This interaction facilitates the formation of C-H bonds and the energy gap opening, which are revealed by angle-resolved photoemission spectroscopy (ARPES) and density-functional theory (DFT) in this study. In agreement with theoretical prediction, the atomic percentage of hydrogen on graphene by chemisorption is higher than physisorption. We also obtain the utilization efficiency for chemisorption hydrogen storage through Ti decoration, and this efficiency is higher than the uptake capacity in Pd decoration. This study provides a pathway for applications towards hydrogen adsorbate-induced modification of electronic structure in graphene.

Keywords: Decorated graphene, Electronic evidence, Spillover effect, ARPES, DFT